Law Firm Engagement for PSI and DSI of a Former Service Station, Inner Sydney, NSW

Project overview

iEnvi was engaged by a law firm to undertake a confidential preliminary site investigation (PSI) and subsequent detailed site investigation (DSI) focused on an underground petroleum storage system (UPSS) at a commercial property in inner Sydney. The property comprised a shop front and a workshop occupied by a business operating 8:00–17:00 Monday to Friday. The client required the investigation to be carried out with minimal disruption to trading and without damaging a recently renovated shopfront.

What we did

• Desk review and historical records search to confirm likely UPSS locations and past filling activities.
• Non‑intrusive location (potholing and geophysics) and careful removal of small flooring sections to locate UPSS tanks beneath the shop floor.
• Installation of groundwater monitoring wells to allow sampling and ongoing monitoring.
• Collection of soil samples from multiple boreholes to depths of up to 3 m across the site.
• Installation of vapour pins and collection of soil vapour samples to assess potential vapour intrusion risk to indoor spaces and future sensitive land uses.
• Laboratory analysis and interpretation against national assessment levels and site‑specific risk context.

Key findings

• Hydrocarbon contamination consistent with historical UPSS use was detected in soil, groundwater and soil vapour.
• There is evidence that historical fill activities have contributed to the extent of contamination in places across the site.
• For continued commercial use the site risk could be managed by controls and monitoring; however, conversion to residential use would likely require remediation and validation to meet residential protection levels.

Commercial and legal outcomes

The investigation report delivered a clear conceptual site model, described the human‑health and environmental risks associated with the soil, groundwater and vapour concentrations observed, and provided a recommended scope and order‑of‑magnitude approach for remediation or management. The report is being used in legal proceedings to quantify property impairment and iEnvi staff are available to provide expert witness services and technical advice.

Practical takeaways for vendors, purchasers and developers

• Former service stations and long‑lived UPSS installations commonly create petroleum hydrocarbon impacts to soil, groundwater and vapour — early intrusive investigation limits transaction and development risk.
• Risk and compliance outcomes are land‑use sensitive: residential uses typically require more conservative assessment levels and may trigger remediation obligations where commercial assessment levels would not. Planning and transaction teams should allow time and budget for DSI, remediation design and validation if a sensitive use is proposed.
• Careful investigation design and sensitive intrusive works enable investigation in occupied retail/workshop premises while protecting trading and finished fitout areas.

Next steps we typically recommend

1. Confirm target land use and regulatory requirements with the client and relevant consent authority.
2. If residential use is proposed, prepare a remediation options analysis and costed remediation strategy, including an implementation program and validation strategy.
3. Where legal matters require it, prepare peer‑reviewable expert reports and be available for expert witness or mediation support.

Confidential advice and expert support

If you need a fast, technically robust PSI or DSI for legal liability, development approval, finance or due‑diligence purposes, contact an iEnvi specialist for a confidential discussion. Call 1300 043 684 or contact us for a private enquiry about your site.